Redox flow batteries are promising energy storage and conversion systems for stationary applications. Performance of bipolar plates as well as their cost and weight has important contribution to the development of redox flow batteries. Electrically conductive polymer composites are alternatives to graphite and metallic bipolar plates. These composites combine process benefits of polymers with electrically conductive nature of carbonaceous fillers and exhibit advantages of light-weight, ease of machining and good corrosion resistance. Bipolar plates require high electrical conductivity, good mechanical properties and chemical stability. In order to achieve these goals, thermoplastics and carbon derivatives were chosen as matrix material and filler respectively. Carbon nanotube based composites possessed improved electrical conductivities and mechanical strength. Processing of highly filled composites was facilitated by using additives during melt mixing. Produced bipolar plates were tested in all-vanadium redox flow battery single-cell in order to evaluate their potential to be used in up-scale applications.